(a) Field of the Invention
The present invention relates to a rechargeable battery. In particular, the present invention relates to a rechargeable battery module that has an improved arrangement of unit batteries that minimizes the overall volume of the rechargeable battery module when the unit batteries are connected to form the rechargeable battery module.
(b) Description of the Related Art
In recent years, high-power rechargeable batteries that use non-aqueous electrolytes that have high energy densities have been developed. For example, a plurality of high-power rechargeable batteries may be connected together in series to form a large-scale rechargeable battery that can drive a motor in a high-power apparatus such as an electric vehicle and the like.
A single large-scale rechargeable battery, referred to as a battery module, generally comprises a plurality of rechargeable batteries, referred to as unit batteries that are connected to each other in series. Each of the unit batteries includes an electrode assembly that comprises an anode and a cathode with a separator interposed therebetween, a case that has a space for housing the electrode assembly, a cap assembly that is combined with the case to cover the case, and an anode terminal and a cathode terminal that are coupled with collectors of the anode and the cathode in the electrode assembly, respectively.
In a rectangular unit battery, the anode terminal and the cathode terminal that project from the cap assembly are generally arranged alternately with the anode terminal and the cathode terminal of an adjacent unit battery. Then, conductors, such as nuts, are provided between the screw-shaped anode terminals and cathode terminals, thereby forming the battery module.
A battery module has several to tens of unit batteries that are connected to each other. The battery module may have a cooling structure to remove the heat that is generated in the respective unit batteries, a safety unit, a system circuit, and the like. The addition of these components results in an increase in the volume of the battery module.
In order to reduce the size of the battery module, a technique to reduce a gap between the unit batteries has been suggested. This technique has the drawback of making it difficult to dissipate heat that is generated in the respective unit batteries.
A critical design feature of a battery module is to allow it to easily dissipate the heat that is generated in the respective unit batteries while maintaining a minimal volume. This feature is especially important for rechargeable batteries that are applied to a hybrid electric vehicle (HEV).
Increased volume of the battery module may also increase, the weight of the battery module itself. For an HEV comprising the battery module, the design thereof becomes difficult.
Further, when the heat is not properly dissipated, the heat from the respective unit batteries may cause an increase in temperature of the battery module. This may cause a malfunction of an apparatus that comprises the battery module.
The demand for a large-scale battery module with a minimal size and superior heat dissipation is increasing for use in HEVs and other apparatuses.